Optical fiber connection component and optical fiber connection structure

ABSTRACT

An optical fiber connecting component includes a glass plate having a plurality of first through holes, a resin ferrule fixed to the glass plate and having a plurality of second through holes that are each coaxial with corresponding one of the plurality of first through holes, and a plurality of optical fibers including a glass fiber and a resin coating that covers the glass fiber. The glass fiber exposed from a tip of each of the optical fibers is held in corresponding one of the first through holes and corresponding one of the second through holes, and a material for the resin ferrule has a flexural modulus of 5 GPa or more at 200° C.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority based on Japanese Patent ApplicationNo. 2019-206145 filed on Nov. 14, 2019, the entire contents of which areincorporated herein by reference.

BACKGROUND ART

The present disclosure relates to an optical fiber connection componentand an optical fiber connection structure.

Patent Document 1 discloses an optical connector including an opticalfiber, a ferrule having a flat ferrule end face facing a counterpartoptical connector and holding the optical fiber, and a spacer providedon the ferrule end face and defining a gap between the ferrule end faceand the counterpart optical connector. According to the opticalconnector of Patent Document 1, by providing a gap between the opticalconnectors with a spacer, it is easy to clean the ferrule end face, andeven when a plurality of optical fibers is connected at the same time, alarge force is not required for the connection, and alignment work iseasy.

Patent Document 2 discloses a multi-fiber connector having a pluralityof optical fiber insertion holes, and suggests that a liquid crystalpolymer or polyphenylene sulfide (PPS) can be used as a resin materialforming the multi-fiber connector, in addition to a polyimide-basedresin.

Patent Document 3 discloses a resin-made optical path conversion elementhaving a structure in which a fiber is bent and fixed while beingpositioned.

CITATION LIST Patent Literature

Patent Document 1: WO 2017/073408 A1

Patent Document 2: JP-A-2004-117616

Patent Document 3: JP-A-2007-147859

SUMMARY OF INVENTION Means for solving the problem

An optical fiber connecting component according to an aspect of thepresent disclosure includes: a glass plate having a plurality of firstthrough holes; a resin ferrule fixed to the glass plate and having aplurality of second through holes that are each coaxial withcorresponding one of the plurality of first through holes; and aplurality of optical fibers including a glass fiber and a resin coatingthat covers the glass fiber, wherein the glass fiber exposed from a tipof each of the optical fibers is held in corresponding one of the firstthrough holes and corresponding one of the second through holes, and amaterial for the resin ferrule has a flexural modulus of 5 GPa or moreat 200° C.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an external perspective view illustrating an optical fiberconnecting component according to the present disclosure.

FIG. 2 is an exploded perspective view of the optical fiber connectingcomponent of FIG. 1 .

FIG. 3 is a view illustrating a front face of a multi-hole glass plateincluded in the optical fiber connecting component of FIG. 1 .

FIG. 4 is a cross-sectional view taken along line IV-IV of the opticalfiber connecting component illustrated in FIG. 1 .

FIG. 5 is a conceptual diagram for explaining a glass fiber disposedbetween a glass plate and a resin ferrule in the optical fiberconnecting component of FIG. 1 .

FIG. 6 is a graph showing deformation of a resin ferrule according to anexample and a resin ferrule according to a comparative example when heattreatment is performed.

FIG. 7 is a graph showing deformation of a multi-hole glass plate whenan optical fiber connecting component using a resin ferrule according toan embodiment is heat-treated.

FIG. 8 is a front view of an optical fiber connecting componentaccording to a first modification.

FIG. 9 is a diagram illustrating an optical fiber connecting componentaccording to a second modified example.

FIG. 10 is a schematic cross-sectional view illustrating a glass platemain body included in the optical fiber connecting component of FIG. 9 .

FIG. 11 is a diagram illustrating an optical fiber connecting componentaccording to a third modified example.

FIG. 12 is a conceptual diagram illustrating an optical fiber connectingcomponent according to a fourth modified example.

DESCRIPTION OF EMBODIMENTS

[Problems to be Solved by Present Disclosure]

In the optical connector of Patent Document 1, a ferrule formed of aresin material has a structure having a plurality of holes, and thus twodimensional arrangement of optical fibers is possible. However, there isroom for improvement in heat resistance.

Patent Document 2 suggests that a liquid crystal polymer havingexcellent heat resistance is used as an optical connector material.Since the liquid crystal polymer has higher molding anisotropy than PPSgenerally used for an optical connector, it is difficult to manufacturea ferrule for an optical connector requiring high hole forming accuracyby using only the liquid crystal polymer.

In Patent Document 3, the optical path conversion element is formed ofan element main body made of resin and having a block shape with anL-shaped cross section. In a case where the positioning structure of thetip end of the fiber is formed of a resin material, ultraviolet rayscannot be transmitted, and thus, for example, the optical pathconversion element and a silicon-photonic integrated circuit (Si-PIC)formed on Si such as silicon photonics cannot be bonded and fixed toeach other using a UV adhesive.

An object of the present disclosure is to provide an optical fiberconnecting component and an optical fiber connecting structure capableof improving heat resistance and enabling high-definition arrangement ofoptical fibers.

[Advantageous Effects of Present Disclosure]

According to the present disclosure, it is possible to provide anoptical fiber connecting component that improves heat resistance andenables high-definition arrangement of optical fibers.

[Description of Embodiments of the Present Disclosure]

An overview of embodiments of the present disclosure will be described.

(1) An optical fiber connecting component includes a glass plate havinga plurality of first through holes, a resin ferrule fixed to the glassplate and having a plurality of second through holes that are eachcoaxial with corresponding one of the plurality of first through holes,and a plurality of optical fibers including a glass fiber and a resincoating that covers the glass fiber. The glass fiber exposed from a tipof each of the optical fibers is held in corresponding one of the firstthrough holes and corresponding one of the second through holes, and amaterial for the resin ferrule has a flexural modulus of 5 GPa or moreat 200° C. Here, “coaxial” means a positional relationship in which thecentral axes of the respective objects coincide with each other.

According to the above configuration, since the optical fiber connectingcomponent has heat resistance as a whole and the first through hole canbe formed with high definition in the glass plate, for example, highlyaccurate positioning capable of connecting a single-mode optical fibercan be realized. In addition, since the glass plate fixing the glassfiber can transmit ultraviolet rays, a UV adhesive can be used when anoptical fiber connecting component is connected to an optical integratedcircuit such as a Si-PIC.

(2) An example of the material is a liquid crystal polymer.

By using a liquid crystal polymer as the resinous material constitutingthe resin ferrule, the flexural modulus of the resin ferrule can be 5GPa or more (for example, 10 GPa, 20 GPa, 30 GPa, or 50 GPa) at 200 ° C.

(3) The material preferably has a thermal shrinkage of 0.5% or less (forexample, 0.05%, 0.1%, 0.3%, or 0.4%) upon heating from room temperatureto a temperature of 200° C. or higher.

When the thermal deformation of the glass plate is large, there is apossibility that the inclination of the connected optical fiber changesand optical loss occurs. On the other hand, according to theabove-described configuration, since the resin ferrule having a smallthermal shrinkage rate is used, it is possible to suppress deformationof the glass sheet caused by deformation of the resin ferrule.Accordingly, when a plurality of optical fibers fixed to an opticalfiber connecting component are connected to a plurality of opticalfibers fixed to another optical fiber connecting component, it ispossible to suppress the occurrence of optical loss due to theinclination of the connected optical fibers.

(4) It is preferable that the plurality of optical fibers held in theplurality of first through holes and the plurality of second throughholes have a variation (standard deviation) in inclination of 0.5 degreeor less (for example, 0.3 degrees, 0.1 degrees, 0.01 degrees, or 0.005degrees). Here, the “inclination of each of the plurality of opticalfibers” is an angle between a direction obtained by averaging thedirections of the plurality of optical fibers and the direction of eachoptical fiber.

By setting the variation in the inclination of the aligned opticalfibers to be within the above-described range, it is possible tosuppress the occurrence of deviation in the direction between theoptical axis of the glass fiber and the optical axis of the fiber of theconnection partner, and it is possible to realize low-loss connectionwith the connection partner (for example, an Si-PIC chip).

(5) It is preferable that the glass plate has a front face that has aP-V value (a difference between a maximum value and a minimum value) of5 μm or less (for example, 0.3 μm, 0.1 μm, 0.01 μm, or 0.005 μm) whenthe glass plate is heated at 200° C. or higher.

When the thermal deformation of the glass plate is within the aboverange, the occurrence of light loss can be suppressed.

(6) It is preferable that the plurality of first through holes istwo-dimensionally arranged at one section of the glass plate.

According to the above configuration, a larger number of optical fiberscan be mounted as compared with the case of using a conventionalV-groove substrate, and the fiber mounting density is improved.

(7) It is preferable that the glass fiber protrudes from an end face ofthe glass plate by 50 nm to 1 μm.

According to the above configuration, the glass fiber and the fiber ofthe connection partner can be connected by PC (Physical Contact)connection.

(8) It is preferable that the glass plate has a first guiding hole, andthe resin ferrule has a second guiding hole that is coaxial with thefirst guiding hole.

According to the above configuration, by using the first guiding holeand the second guiding hole, positioning of the first through hole ofthe glass plate and the second through hole of the resin ferrule isfacilitated.

(9) It is preferable that the glass fiber has an outer diameter of 100μm or less (for example, 95 μm, 80 μm, 50 μm, or 40 μm).

According to the above configuration, it is possible to reduce a strainwhen the optical fiber is bent and fixed within the resin ferrule. Thus,a space-saving optical fiber connecting component having a low overallheight can be provided. In addition, it is possible to suppress tensilestrain and compressive strain when the glass fiber is bent, and it isalso possible to contribute to preventing disconnection of the glassfiber.

(10) It is preferable that each of the plurality of optical fibers is amulti-core optical fiber the glass fiber of which includes a pluralityof cores and a cladding that surrounds the plurality of cores.

According to the above configuration, an optical fiber connectingcomponent having a high core density can be realized.

(11) In the optical fiber connection structure of the presentdisclosure, a first optical fiber connecting component serving as theoptical fiber connecting component according to any one of Item (1) toItem (10) and a second optical fiber connecting component fixed to thefirst optical connecting component and having a plurality of opticalfibers in an arrangement corresponding to an arrangement of theplurality of optical fibers in the first optical fiber connectingcomponent are connected. A first end face of the first optical fiberconnecting component and a second end face of the second optical fiberconnecting component are faces inclined with respect to an optical axisof the plurality of optical fibers, and a gap of 30 μm or less is formedbetween the first end face and the second end face.

According to the above-described configuration, favorable opticalconnection is possible, and additional processing for protruding theglass fiber from the end face of the glass plate is unnecessary.

(12) It is preferable that the second optical fiber connecting componentis the optical fiber connecting component according to any one of Item(1) to Item (10), a spacer for forming the gap is provided at an endface of the glass plate of at least one of the first optical fiberconnecting component and the second optical fiber connecting component.

(13) It is preferable that the second optical fiber connecting componentis provided by mounting the plurality of optical fibers in a resinferrule, and a spacer for forming the gap is provided at an end face ofthe second optical fiber connecting component.

(14) It is preferable that the optical fiber connection structurefurther includes an adapter, the adapter fitting to the first opticalfiber connecting component and the second optical connecting componentso as to connect the first optical fiber connecting component and thesecond optical fiber connecting component, the second optical fiberconnecting component is the optical fiber connecting component accordingto any one of Item (1) to Item (10) or a component provided by mountingthe plurality of optical fibers in a resin ferrule, and a spacer forforming the gap is provided in the adapter of the optical fiberconnecting structure.

It is preferable that a spacer for providing a gap between the first endface and the second end face is provided in the configuration of any oneof Items (12) to (14).

[Details of Embodiments of the Present Disclosure]

Hereinafter, embodiments of the present disclosure will be describedwith reference to the drawings. Members having the same referencenumerals as those already described in the description of the presentembodiment will not be described for convenience of description. Inaddition, the dimensions of each member illustrated in the drawings maybe different from the actual dimensions of each member for convenienceof description.

In addition, in the description of the present embodiment, in order tofacilitate understanding of the present embodiment, an X-axis, a Y-axis,and a Z-axis orthogonal to each other are referred to as appropriate.These directions are relative directions set in an optical fiberconnecting component 1 illustrated in FIG. 1 . Therefore, along with therotation of optical fiber connecting component 1, the X-axis, theY-axis, and the Z-axis are also rotated.

First Embodiment

Optical fiber connecting component 1 according to the first embodimentwill be described below with reference to FIGS. 1 to 5 . FIG. 1 is anexternal perspective view illustrating optical fiber connectingcomponent 1. FIG. 2 is an exploded perspective view of optical fiberconnecting component 1 of FIG. 1 . FIG. 3 is a view illustrating a frontface of a glass plate included in optical fiber connecting component 1illustrated in FIG. 1 . FIG. 4 is a cross-sectional view taken alongline IV-IV of optical fiber connecting component 1 illustrated in FIG. 1. FIG. 5 is a conceptual diagram for explaining a glass fiber disposedbetween a glass plate and a resin ferrule in optical fiber connectingcomponent 1 of FIG. 1 in relation to FIG. 4 . Optical fiber connectingcomponent 1 is used to optically connect, for example, an electronicsubstrate including an optical integrated circuit chip or the like and alocal wiring (or an external transmission line).

As illustrated in FIG. 1 , optical fiber connecting component 1 includesoptical fibers 10 and optical fibers 10 a arranged side by side withoptical fibers 10. Each of the optical fibers 10 and 10 a has, forexample, a bending portion (bending portion 13) in the middle thereof.One end of optical fibers 10 and 10 a is fixed to an electronicsubstrate via a fiber fixing part 20, and the other end of opticalfibers 10 and 10 a is connected to a local wiring via a connector (notillustrated).

As shown in FIG. 2 , optical fibers 10 and 10 a includes a plurality ofglass fibers 11 arranged along the Y direction shown in the drawing.Each of the glass fibers 11 includes a core made of silica-based glassand a cladding surrounding the core. The outer diameter of glass fibers11 is, for example, 100 μtm or less. Optical fibers 10 and 10 a may be asingle-core optical fiber including a glass fiber having a single coreand a cladding surrounding the single core, or may be a multi-coreoptical fiber including a glass fiber having a plurality of cores and acladding collectively surrounding the plurality of cores.

An individual coating resin layer 12 is provided on the outside of eachof glass fibers 11. In addition, the periphery of individual coatingresin layer 12 is covered with a collective coating resin layer 14behind bending portion 13 of glass fibers 11 (in the positive directionof X illustrated in the drawing).

Note that glass fibers 11 are desirably a low bending loss fiber inorder to be able to cope with a flexible bending shape. For a lowbending loss fiber, preferable is a fiber in which confinement of lightto the core is strengthened by applying a structure in which therefractive index of the core is increased or a refractive indexstructure called a trench structure. The composition of glass fibers 11can be prepared by adding a dopant for appropriately controlling therefraction index using SiO₂ glass. For example, the core may be made ofSiO₂ glass to which GeO₂ is added or SiO₂ glass to which GeO₂ and F areco-added. The cladding may be made of pure SiO₂ glass or SiO₂ glassdoped with fluorine. This makes it possible to obtain an optical fiberthat is economical and has good shape controllability.

In addition, in order to increase the strength of the optical fiber, itis possible to suitably combine a method of performing carbon coating onthe outer periphery of glass fibers 11, a method of applying compressivestrain to the outer periphery of glass fibers 11 by adjusting thermalhistory during drawing, or the like. Bent optical fibers 10 and 10 aillustrated in FIG. 1 may be heated and bent in advance. In this case,glass fibers 11 in bending portion 13 are exposed before heating. As theheating means, a burner, a CO₂ laser, an arc discharge, a heater or thelike can be used.

Since the CO₂ laser can easily adjust the irradiation intensity, theirradiation range, and the irradiation time, it has advantageouscharacteristics for precise control of the distribution of curvatures.In the vicinity of 10 μm, which is a typical wavelength of a CO₂ laser,since glass is opaque, it is considered that the irradiation energy ofthe CO₂ laser is absorbed by the surface layer of glass fibers 11 and istransmitted by re-radiation and thermal conduction. If the power of theCO₂ laser is too high, the surface layer temperature of glass fibers 11rises sharply to the temperature at which the glass evaporates, and theshape cannot be maintained. For this reason, the irradiation power ofthe CO₂ laser is appropriately adjusted so that the glass in the surfacelayer of glass fibers 11 does not evaporate and the cross section of theheated glass fibers 11 rises to a temperature equal to the working point(10⁴ dPa·sec) or more for a predetermined time to remove the strain. Itis desirable that the cooling rate of the temperature of glass fibers 11when bent by the CO₂ laser is 10⁴° C./s or less, and glass fibers 11 arecooled slowly in order to remove distortion.

Fiber fixing part 20 includes a multi-hole glass plate 21 (an example ofa glass plate) and a multi-hole resin ferrule 31 (an example of a resinferrule). As illustrated in FIG. 2 , multi-hole glass plate 21 has aglass plate main body 22 having, for example, a rectangularparallelepiped shape. Glass plate main body 22 is transparent toultraviolet rays. A rectangular front face 23 of glass plate main body22 is disposed to face a rear face 34 of multi-hole resin ferrule 31. Arectangular rear face 24 of glass plate main body 22 is disposed to facethe electronic substrate.

The thickness between front face 23 and rear face 24 of glass plate mainbody 22 (the width in the Z direction in the drawing) is as thin as 1mm,for example, and glass plate main body 22 has a plurality of firstthrough holes 25 penetrating through front face 23 and rear face 24. Asillustrated in FIG. 3 , the plurality of first through holes 25 are, forexample, two dimensionally arranged along the width direction (Ydirection in the drawing) and the length direction (X direction in thedrawing) of glass plate main body 22. Glass fibers 11 are held in firstthrough holes 25.

First through holes 25 can be formed by, for example, a process in whichphotolithography and dry etching such as reactive ion etching (RIE) arecombined, or a drilling technique using a laser. For example, thepositional accuracy of first through holes 25 is preferably ±1 μm orless. Note that the technique is not limited to the above-describedtechnique as long as the technique is a glass hole forming techniquecapable of realizing that the position of first through holes 25 has anerror of 1 μm or less with respect to a predetermined design positionand the inner diameter of first through holes 25 is ±1 μm or less withrespect to a predetermined diameter. In this example, an example inwhich glass plate main body 22 has a plurality of first through holes 25has been described, but the number of first through holes may be one.

Guiding holes 26 are provided in the vicinity of both ends of glassplate main body 22 when viewed in the Y direction illustrated in thedrawing. As illustrated by a broken line in FIG. 2 , multi-hole resinferrule 31 has guiding holes 37 at positions corresponding to guidingholes 26 of glass plate main body 22. By inserting guide pins 45 intoguiding holes 26 of glass plate main body 22 and guiding holes 37 ofmulti-hole resin ferrule 31, respectively, first through holes 25 andsecond through holes 38 of multi-hole resin ferrule 31, which will bedescribed with reference to FIG. 4 , can be easily aligned in a coaxialrelationship.

Guide pins 45 may be pulled out from multi-hole glass plate 21 andmulti-hole resin ferrule 31 after multi-hole glass plate 21 andmulti-hole resin ferrule 31 are fixed. This is because if guide pins 45are left without being pulled out, multi-hole glass plate 21 may bedamaged if the difference between the thermal expansion coefficient ofmulti-hole glass plate 21 and the thermal expansion coefficient ofmulti-hole resin ferrule 31 is large.

As illustrated in FIG. 1 , multi-hole resin ferrule 31 has a ferrulemain body 32 that is substantially L-shaped in a side view, and isplaced on multi-hole glass plate 21. As illustrated in FIG. 2 , ferrulemain body 32 has a front face 33 on which optical fibers 10 a can beplaced, and rear face 34 disposed on one end side of front face 33 so asto face front face 23 of glass plate main body 22. A front wall 35facing bending portion 13 of optical fibers 10 and 10 a is provided atone end of front face 33 of ferrule main body 32. In addition, sidewalls36 are provided on the sides of front face 33 of ferrule main body 32 soas to face the side ends of optical fibers 10 and 10 a.

As illustrated in FIG. 4 , the height (the height in the Z direction inthe drawing) of ferrule main body 32 from front face 33 to rear face 34is greater than the height (1 mm) of glass plate main body 22 from frontface 23 to rear face 24. Ferrule main body 32 has a plurality of secondthrough holes 38 passing through front face 33 and rear face 34. As wellas the first through holes 25, the second through holes 38 are twodimensionally arranged along the width direction (the Y direction in thedrawing) and the length direction (the X direction in the drawing) offerrule main body 32. As well as in the first through holes 25, theglass fibers 11 are held in the second through holes 38.

Second through holes 38 have, near front face 33 of ferrule main body32, fiber holding holes 39 in which individual coating resin layer 12 ofthe optical fibers can be loosely fitted. The outer diameters of firstthrough holes 25 and second through holes 38 are larger than the outerdiameter of glass fibers 11 exposed from the distal end of the opticalfibers.

In the present embodiment, an example of multi-hole resin ferrule 31having the substantially L-shaped ferrule main body 32 has beendescribed. However, various shapes can be adopted for portions otherthan rear face 34 disposed to face front face 23 of glass plate mainbody 22. The multi-hole resin ferrule is not limited to the shapeapplicable to the bent optical fibers illustrated in FIG. 1 , forexample, and may be a shape applicable to linear optical fibers that arenot bent.

As illustrated in FIG. 4 , ferrule main body 32 has a protrusion 40protruding toward glass plate main body 22 at an outer peripheralportion of rear face 34. Protrusion 40 is fixed in contact with frontface 23 of multi-hole glass plate 21, so that the opening of firstthrough holes 25 located on front face 23 of multi-hole glass plate 21and the opening of second through holes 38 located on rear face 34 ofmulti-hole resin ferrule 31 are spaced apart from each other by apredetermined distance (indicated by H in FIG. 4 ). For example, an airgap 42 is present around glass fibers 11 located between front face 23of multi-hole glass plate 21 and rear face 34 of multi-hole resinferrule 31 or in a region between adjacent glass fibers 11 excluding theperiphery of glass fibers 11. Note that the region between the adjacentglass fibers 11 excluding the periphery of the glass fibers 11 may befilled with resins having a Young modulus of 100 MPa or less.

Meanwhile, if the front face of the multi-hole glass plate and the rearface of the multi-hole resin ferrule are brought into contact with eachother without a gap, a shear force may be applied to the glass fiber inaccordance with a temperature change due to a difference between athermal expansion coefficient of the multi-hole glass plate and athermal expansion coefficient of the multi-hole resin ferrule, and theglass fiber may be broken.

On the other hand, in the present embodiment, front face 23 ofmulti-hole glass plate 21 and rear face 34 of multi-hole resin ferrule31 are spaced apart from each other by a predetermined distance H,thereby allowing glass fibers 11 to be bent. Therefore, as illustratedin FIG. 5 , even when the position of first through holes 25 ofmulti-hole glass plate 21 and the position of second through holes 38 ofmulti-hole resin ferrule 31 corresponding to first through holes 25 aredisplaced with a change in temperature, a shear force is hardly appliedto glass fibers 11. Therefore, it is possible to prevent disconnectionof glass fibers 11 between first through holes 25 and second throughholes 38. In addition, since the outer diameters of first through holes25 and second through holes 38 are larger than the outer diameter ofglass fibers 11, even if the temperature of optical fiber connectingcomponent 1 changes in the range of −40° C. to 85° C., which is usuallyused, contact between first through holes 25 and second through holes 38and glass fibers 11 can be easily avoided, which also contributes toprevention of disconnection of glass fibers 11.

First through holes 25 provided in glass plate main body 22 have astraight portion 25 a for holding glass fibers 11 and a tapered portion25 b whose diameter increases toward front face 23 of glass plate mainbody 22. Similarly, second through holes 38 provided in ferrule mainbody 32 have a straight portion 38 a for holding glass fibers 11 and atapered portion 38 b whose diameter increases toward rear face 34 offerrule main body 32. By providing the tapered portions 25 b and 38 b inthis manner, as illustrated in FIG. 5 , the distance between the openingof first through holes 25 and the opening of second through holes 38 islarger than the distance H from front face 23 of glass plate main body22 to rear face 34 of the rule main body 32 by the tapered portions 25 band 38 b. Therefore, the shearing force applied to glass fibers 11 canbe further reduced.

As a resin material constituting multi-hole resin ferrule 31, forexample, a liquid crystal polymer is preferably used. As liquid crystalpolymers, the following examples may be mentioned.

(1) a polycondensate of ethylene terephthalate and p-hydroxybenzoicacid;

(2) a polycondensate of phenol, phthalic acid (for example, 4,4-dihydroxybiphenol, terephthalic acid), and parahydroxybenzoic acid;

(3) a polycondensate of polyarylate, for example, 2, 6-hydroxynaphthoicacid and parahydroxybenzoic acid;

It is desirable that an inorganic filler is kneaded into the liquidcrystal polymer in order to improve anisotropy and low weld strength. Asthe inorganic filler, a spherical or fibrous glass filler can bepreferably used.

Since the liquid crystal polymer has a glass transition point of 90° C.or higher, it is not denatured in a region of −40° C. to +85° C. inwhich optical fiber connecting component 1 is usually used, and has highdurability against humidity. In addition, by using the above-describedliquid crystal polymer as the resinous material of multi-hole resinferrule 31, it is possible to achieve a flexural modulus of multi-holeresin ferrule 31 of 5 GPa or more at 200° C., more preferably 5 GPa ormore at 260° C.

The liquid crystal polymer has good fluidity and is relatively easy tomold. Since multi-hole resin ferrule 31 using the liquid crystal polymercan be formed into various shapes, it is possible to easily meet therequirements for optical fiber connecting component 1 such as changingthe optical path direction and reducing the height of optical fiberconnecting component 1.

FIG. 6 is a graph showing deformation of a multi-hole resin ferruleaccording to an embodiment made of a liquid crystal polymer (LCP) and amulti-hole resin ferrule according to a comparative example made ofpolyphenylene sulfide (PPS), which is a conventional material, when heattreatment is performed at 260° C. for 5 minutes. FIG. 6 is a graphshowing the unevenness of the end face of the resin ferrule according tothe example and the comparative example.

As shown in FIG. 6 , in the comparative example using PPS, theunevenness of the end face of the multi-hole resin ferrule was 12 μm ormore in P-V (Peak-Valley) value. Since PPS, which is an existing resinferrule material, has a glass transition point of about 90° C.,deformation after heat treatment is large. When a multi-hole glass plateis attached to such a resin material having large thermal deformationand heat treatment is performed, large deformation is also given to themulti-hole glass plate after heat treatment. Here, the P-V value is asum of a distance from an average plane approximating the end face ofthe multi-hole resin ferrule to a most protruding point and a mostrecessed point. The end face shape of the multi-hole resin ferrule canbe obtained by using an optical surface roughness/shape measuringmachine using an interference microscope, and the average plane can bedetermined from the end face shape by using a least square method.

On the other hand, in the example using the liquid crystal polymer, theunevenness of the end face of the multi-hole resin ferrule was 5 μm orless in P-V value. It was confirmed that, by using a liquid crystalpolymer having excellent heat resistance as a resin ferrule material,even when heat treatment is performed at a general reflow temperature of260° C., thermal deformation can be significantly suppressed as comparedwith PPS. Specifically, by using the liquid crystal polymer, it ispossible to suppress the thermal shrinkage of the multiple-hole resinferrule to 0.5% or less upon heating from room temperature (for example,20° C.) to a temperature of 200° C. or higher, preferably from roomtemperature to 260° C. or higher.

FIG. 7 is a graph showing deformation of a multi-hole glass plate whenan optical fiber connecting component including a multi-hole resinferrule and a multi-hole glass plate using a liquid crystal polymeraccording to an embodiment is heat-treated at 260° C. for 5 minutes. Asshown in FIG. 7 , the unevenness of the end face of the multi-hole glassplate after the heat treatment was about 0.5 μm in terms of P-V value,and it was possible to achieve 5 μm in terms of P-V value and preferably1 μm in terms of P-V value, which are deformation amount sufficientlyallowable for securing the positional accuracy of the fiber.

As described above, optical fiber connecting component 1 according tothis embodiment includes multi-hole glass plate 21 having a plurality offirst through holes 25, multi-hole resin ferrule 31 fixed to multi-holeglass plate 21 and having a plurality of second through holes 38 coaxialwith the first through holes 25, and a plurality of optical fibers 10and 10 a including glass fibers 11 held in first through holes 25 andsecond through holes 38. Multi-hole resin ferrule 31 is made of aresinous material having a flexural modulus of elasticity of 5 GPa ormore at 200° C. In order to realize a flexural modulus of 5 GPa or moreat 200° C., a liquid crystal polymer is used as a resinous materialconstituting multi-hole resin ferrule 31. As a result, the heatresistance of entire optical fiber connecting component 1 can beimproved. In addition, by using multi-hole resin ferrule 31 that canhave a flexible shape, it is possible to protect optical fibers 10 and10 a and fix the bent shape.

Further, since the positioning structure for the optical integratedcircuit is formed by multi-hole glass plate 21, the position anddiameter of the long through-hole can be formed with high accuracy.Therefore, first through holes 25 can be arranged two dimensionally withrespect to multi-hole glass plate 21, and optical fiber connectingcomponent 1 with high-channel-density can be obtained. In particular,when the size of multi-hole glass plate 21 is S and the number ofmounted fibers is n, it is possible to obtain a high-channel-densityoptical fiber connecting component 1 in which n/S exceeds 10/mm². Inaddition, as described above, since multi-hole glass plate 21 istransparent to ultraviolet rays, multi-hole glass plate 21 can be fixedto an electronic substrate, for example, an optical integrated circuitsuch as an Si-PIC by using a UV adhesive.

Meanwhile, when thermal deformation of the multi-hole glass plate islarge, optical loss may occur in coupling between a glass fiber includedin an optical fiber connecting component and a silicon photonics chip(SiPH chip). The deformation of the multi-hole glass plate becomes asignificant problem particularly when realizing a multi-channel opticalfiber connecting component of 100 ch or more that requires an increasein the size of the multi-hole glass plate. However, the thermaldeformation of the multi-hole glass plate is not caused by the glassplate itself, but is mainly caused by the thermal deformation of themulti-hole resin ferrule.

On the other hand, in optical fiber connecting component 1 according tothis embodiment, multi-hole resin ferrule 31 made of a liquid crystalpolymer which is a resin material having a thermal shrinkage of 0.5% orless upon heating from room temperature to 200° C. or higher, preferablyfrom room temperature to 260° C. or higher is used. Therefore, thermaldeformation can be significantly suppressed as compared with theexisting multi-hole resin ferrule using PPS. By suppressing the thermaldeformation of multi-hole resin ferrule 31, the deformation amount ofmulti-hole glass plate 21 after heat treatment is also suppressed to 5μm or less, preferably 1 μm or less in terms of P-V value. Therefore,the deviation in direction between the optical axis of glass fibers 11and the optical axis of the fibers to be connected, that is, thecoupling angle difference between the channels, can be maintained at asubstantially negligible level.

According to the present embodiment, since the deformation amount ofmulti-hole glass plate 21 after the heat treatment is small, thevariation in inclination (angular variation) of glass fibers 11 fixed tomulti-hole glass plate 21 is 0.5 degrees or less. As a result, thedifference in coupling angle between glass fibers 11 and the SiPh chipis suppressed, and the occurrence of optical loss can be suppressed. Asa result, it is possible to suppress a decrease in coupling efficiencybetween the grating coupler, which is generally used as a front facecoupling method of the SiPh chip, and optical fibers 10 and 10 a.

In the present embodiment, optical fibers 10 and 10 a may be amulti-core optical fiber including glass fiber 11 having a plurality ofcores and a cladding surrounding the plurality of cores. By applying themulti-core optical fiber, for example, it is possible to cope with aform in which high-density input/output of light, specifically exceeding100 ch from one Si-PIC. is required.

(First Modification)

FIG. 8 is a front view of an optical fiber connecting component 1Aaccording to a first modification. As in optical fiber connectingcomponent 1A illustrated in FIG. 8 , glass fibers 11 held in firstthrough holes 25 of multi-hole glass plate 21 may protrude from rearface 24 of multi-hole glass plate 21. In this case, the protrusionamount of glass fibers 11 from rear face 24 of multi-hole glass plate 21is, for example, about 50 nm to 1 μm. As described above, since glassfibers 11 protrudes from rear face 24 of multi-hole glass plate 21, anend face of glass fibers 11 can be connected to glass fibers protrudingfrom an optical connector on a connection partner side by physicalcontact (PC). However, since the composition of multi-hole glass plate21 used in the present embodiment is substantially the same as that ofglass fibers 11, it is difficult to protrude glass fibers 11 frommulti-hole glass plate 21 by a typical polishing process used in aconventional resin ferrule. Therefore, in order to protrude glass fibers11, additional processing such as laser processing or etching processingof rear face 24 of multi-hole glass plate 21 is required.

(Second Modification)

In the above-described first embodiment, an example of a state in whichfirst through holes 25 extend in the vertical direction (the Z directionin the drawing) with respect to rear face 24 (and front face 23) ofglass plate main body 22 has been described, but the present inventionis not limited to this example.

FIG. 9 is a conceptual diagram illustrating an optical fiber connectingcomponent according to a second modified example. FIG. 9 illustrates anoptical fiber connecting component 1B and an optical fiber connectingcomponent 1C that is a connection partner of optical fiber connectingcomponent 1B. In FIG. 9 , for the sake of explanation, only glass platemain bodies 22B and 22C and the portion of glass fibers 11 held by glassplate main bodies 22B and 22C are illustrated as cross-sectional views.

In optical fiber connecting component 1B illustrated in FIG. 9 , a rearface 24B (an example of a first end face) of a multi-hole glass plate21B is an inclined surface that is not perpendicular to the optical axisof glass fibers 11. Specifically, it is preferable that the angle θformed by the optical axis of glass fibers 11 and rear face 24B ofmulti-hole glass plate 21B is 75 degrees or more and 85 degrees or less.For example, as illustrated in FIG. 10 , multi-hole glass plate 21B hasstraight portion 25 a that is a part of first through holes 25 and isinclined at a certain angle with respect to a line perpendicular to rearface 24B of glass plate main body 22B. Specifically, an angle φ formedby a line perpendicular to rear face 24B of glass plate main body 22Band straight portion 25 a of first through holes 25 is preferably 8degrees.

As well as optical fiber connecting component 1B, a rear face 24C (anexample of a second end face) of a multi-hole glass plate 21C includedin optical fiber connecting component 1C as a connection partner is aninclined surface that is not perpendicular to the optical axis of glassfibers 11. Optical fiber connecting component 1C is a component havingthe same configuration as optical fiber connecting component 1B, andboth the optical fiber connecting components 1B and 1C are fixed to eachother in a state where rear face 24B of multi-hole glass plate 21B ofoptical fiber connecting component 1B and rear face 24C of multi-holeglass plate 21C of optical fiber connecting component 1C are parallel toeach other.

In addition, in order to provide a gap between rear face 24B of opticalfiber connecting component 1B and rear face 24C of optical fiberconnecting component 1C, as illustrated in FIG. 9 , rear face 24B of oneof the optical fiber connecting components 1B and 1C has a spacer 50. Ina state where optical fiber connecting component 1B and optical fiberconnecting component 1C are fixed, the gap formed between the end faceof glass fibers 11 of optical fiber connecting component 1B and the endface of glass fibers 11 of optical fiber connecting component 1C isdefined by the film thickness of spacer 50. The thickness of spacer 50is, for example, 30 μm or less, or preferably 20 μm or less. In thisway, glass fibers 11 of optical fiber connecting component 1B and glassfibers 11 of optical fiber connecting component 1C are disposed so as toface each other via the gap formed between the optical fiber connectingcomponents 1B and 1C, whereby the glass fibers 11 are opticallyconnected to each other.

Like glass plate main body 22B of multi-hole glass plate 21B, it ispreferable that spacer 50 also has heat resistance. Therefore, spacer 50can be formed by, for example, welding a thin film formed of a liquidcrystal polymer or Teflon (registered trademark) on glass plate mainbody 22B. Alternatively, spacer 50 may be formed by selectively etchinga portion of multi-hole glass plate 21B including glass fibers 11 topartially form a concave shape.

As described above, optical fiber connecting components 1B and 1Caccording to the second modification are configured such that rear faces24B and 24C of multi-hole glass plates 21B and 21C are inclined surfacesthat are not perpendicular to the optical axis of glass fibers 11, and agap of 30 μm or less is provided between rear face 24B of optical fiberconnecting component 1B and rear face 24C of optical fiber connectingcomponent 1C to bring them close to each other. Thus, glass fibers 11can be optically connected to each other without performing PCconnection, and low-loss connection can be performed while suppressingFresnel reflection loss. Although the inclination angles of rear faces24B and 24C of glass plate main bodies 22B and 22C differ depending onthe type of optical fiber used, the insertion loss of the optical fiberis 0.5 dB or less and the reflection loss is 40 dB or more (reflectivity0.0001 or less) when a general single-mode optical fiber is used andθ=82° and the gap between optical fiber connecting components 1B and 1C,i.e., the height of spacer 50, is 20 μm.

(Third Modification)

In the second modified example illustrated in FIG. 9 , an example inwhich spacer 50 is provided in glass plate main body 22B of one opticalfiber connecting component 1B of optical fiber connecting components 1Band 1C constituted by a multi-hole glass plate and a multi-hole resinferrule has been described, but the present invention is not limited tothis example. FIG. 11 is a conceptual diagram illustrating an opticalfiber connecting component according to a third modified example. FIG.11 illustrates an optical fiber connecting component 1D and an opticalconnector 100 to which optical fiber connecting component 1D isconnected.

Similar to optical fiber connecting components 1B and 1C according tothe second modification, a rear face 24D of a multi-hole glass plate 21D(a glass plate main body 22D) included in optical fiber connectingcomponent 1D according to the third modification is an inclined surfacethat is not perpendicular to the optical axis of glass fibers 11. As aconnection partner of optical fiber connecting component 1D, opticalconnector 100 using an existing resin ferrule 102 is used. Specifically,optical connector 100 is configured such that an optical fiber is fixedby resin ferrule 102 configured of, for example, PPS. The tip of glassfibers 11 protrudes from the end face of resin ferrule 102 by about 5 μmto 10 μm. An end face 104 of the resin rule 102 has a spacer 106. Asdescribed above, since spacer 106 is provided on end face 104 of resinferrule 102 of optical connector 100 to which optical fiber connectingcomponent 1D is connected, additional processing is not required foroptical fiber connecting component 1D including multi-hole glass plate21D and multi-hole resin ferrule 31 made of a liquid crystal polymer.Also with this configuration, a gap is provided between the end face ofglass fibers 11 of optical fiber connecting component 1D and the endface of the glass fiber of optical connector 100, and the glass fiberscan be brought close to each other. Therefore, the same effects as thoseof the second modified example can be achieved.

(Fourth Modification)

FIG. 12 is a conceptual diagram illustrating an optical fiber connectingcomponent according to a fourth modified example. FIG. 12 illustrates anoptical fiber connecting component 1E, an optical fiber connectingcomponent 1F to which optical fiber connecting component 1E isconnected, and an adapter 60 that holds optical fiber connectingcomponents 1E and 1F in a connected state.

Similar to optical fiber connecting components 1B and 1C of the secondmodification, rear faces 24E and 24F of multi-hole glass plates 21E and21F included in optical fiber connecting components 1E and 1F accordingto the fourth modification are inclined surfaces that are notperpendicular to the optical axis of glass fibers 11. Adapter 60 holdingoptical fiber connecting components 1E and 1F has an opening 61 intowhich optical fiber connecting component 1E and optical fiber connectingcomponent 1F are inserted from both sides, and a spacer 62 is providedinside opening 61 so as to protrude inward at a central portion thereof.As described above, by providing spacer 62 in adapter 60 holding opticalfiber connecting components 1E and 1F, additional processing is notrequired for optical fiber connecting components 1E and 1F. According tothis configuration as well, a gap is provided between the end face ofglass fibers 11 of optical fiber connecting component 1E and the endface of glass fibers 11 of optical fiber connecting component 1F to beconnected, and the glass fibers 11 can be brought close to each other.Therefore, the same effect as that of the second modified example can beachieved.

Although the embodiments of the present disclosure have been describedabove, it is needless to say that the technical scope of the presentinvention should not be restrictively interpreted by the description ofthe embodiments. It is understood by those skilled in the art that thepresent embodiment is merely an example, and various modifications ofthe embodiment can be made within the scope of the invention describedin the claims. As described above, the technical scope of the presentinvention should be determined based on the scope of the inventiondescribed in the claims and the equivalent scope thereof. For example,the material constituting the resin ferrule does not have to be a liquidcrystal polymer as long as it has the physical properties described inthe claims.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1, 1A, 1B, 1C, 1D, 1E, 1F optical fiber connecting component    -   10, 10 a optical fibers    -   11 glass fibers    -   12 individual coating resin layer    -   13 bending portion    -   14 collective coating resin layer    -   20 fiber fixing part    -   21, 21B, 21C, 21D, 21E, 21F multi-hole glass plate (one example        of glass plate)    -   22, 22B, 22C, 22D glass plate main body    -   23, 33 front face    -   24, 24B, 24C, 24D, 24E, 24F, 34 rear face    -   25 first through holes    -   25 a, 38 a straight portion    -   25 b, 38 b tapered portion    -   26, 37 guiding holes    -   31 multi-hole resin ferrule (one example of resin ferrule 102)    -   32 ferrule main body    -   35 front wall (of ferrule main body 32)    -   36 side walls (of ferrule main body 32)    -   38 second through holes    -   39 fiber holding holes    -   40 protrusion    -   42 air gap    -   45 guide pins    -   50, 62, 106 spacer    -   60 adapter    -   61 opening    -   100 optical connector    -   102 resin ferrule    -   104 end face (of resin ferrule 102)

The invention claimed is:
 1. An optical fiber connecting componentcomprising: a glass plate having a plurality of first through holes; aresin ferrule fixed to the glass plate and having a plurality of secondthrough holes that are each coaxial with corresponding one of theplurality of first through holes; and a plurality of optical fibersarranged on a surface of the resin ferrule, one or more glass fibersdisposed within each of the plurality of optical fibers, a surface ofeach of the glass fibers being covered with a resin coating, and aportion of each of the glass fibers being exposed from a tip of each ofthe optical fibers, wherein the exposed portion of each of the glassfibers is held in corresponding one of the first through holes andcorresponding one of the second through holes, and a material for theresin ferrule has a flexural modulus of 5 GPa or more at 200° C.
 2. Theoptical fiber connecting component according to claim 1, wherein thematerial is a liquid crystal polymer.
 3. The optical fiber connectingcomponent according to claim 1, wherein the material has a thermalshrinkage of 0.5% or less upon heating from room temperature to atemperature of 200° C. or higher.
 4. The optical fiber connectingcomponent according to claim 1, wherein the plurality of optical fibersheld in the plurality of first through holes and the plurality of secondthrough holes have a variation in inclination of 0.5 degree or less. 5.The optical fiber connecting component according to claim 1, wherein theglass plate has a front face that has a P-V value of 5 μm or less whenthe glass plate is heated at 200° C. or higher, and wherein the P-Vvalue is a sum of a distance from an average plane approximating an endface of the resin ferrule to a most protruding point and a most recessedpoint of the resin ferrule.
 6. The optical fiber connecting componentaccording to claim 1, wherein the plurality of first through holes istwo-dimensionally arranged at one section of the glass plate.
 7. Theoptical fiber connecting component according to claim 1, wherein theglass fiber protrudes from an end face of the glass plate by 50 nm to 1μm.
 8. The optical fiber connecting component according to claim 1,wherein the glass plate has a first guiding hole, and the resin ferrulehas a second guiding hole that is coaxial with the first guiding hole.9. The optical fiber connecting component according to claim 1, whereinthe glass fiber has an outer diameter of 100 μm or less.
 10. The opticalfiber connecting component according to claim 1, wherein each of theplurality of optical fibers is a multi-core optical fiber including, asthe glass fiber, a plurality of cores and a cladding that surrounds theplurality of cores.
 11. An optical fiber connecting structure in which afirst optical fiber connecting component serving as an optical fiberconnecting component comprising: a glass plate having a plurality offirst through holes; a resin ferrule fixed to the glass plate and havinga plurality of second through holes that are each coaxial withcorresponding one of the plurality of first through holes; and aplurality of optical fibers including a glass fiber and a resin coatingthat covers the glass fiber, wherein the glass fiber exposed from a tipof each of the optical fibers is held in corresponding one of the firstthrough holes and corresponding one of the second through holes, and amaterial for the resin ferrule has a flexural modulus of 5 GPa or moreat 200° C. and a second optical fiber connecting component fixed to thefirst optical connecting component and having a plurality of opticalfibers in an arrangement corresponding to an arrangement of theplurality of optical fibers in the first optical fiber connectingcomponent are connected, wherein a first end face of the first opticalfiber connecting component and a second end face of the second opticalfiber connecting component are faces inclined with respect to an opticalaxis of the plurality of optical fibers, and a gap of 30 μm or less isformed between the first end face and the second end face.
 12. Theoptical fiber connecting structure according to claim 11, wherein thesecond optical fiber connecting component is the optical fiberconnecting component in claim 11, and a spacer for forming the gap isprovided at an end face of the glass plate of at least one of the firstoptical fiber connecting component and the second optical fiberconnecting component.
 13. The optical fiber connecting structureaccording to claim 11, wherein the second optical fiber connectingcomponent is provided by mounting the plurality of optical fibers in aresin ferrule, and a spacer for forming the gap is provided at an endface of the second optical fiber connecting component.
 14. The opticalfiber connecting structure according to claim 11 further comprising anadapter, the adapter fitting to the first optical fiber connectingcomponent and the second optical connecting component so as to connectthe first optical fiber connecting component and the second opticalfiber connecting component, wherein the second optical fiber connectingcomponent is the optical fiber connecting component in claim 11 or acomponent provided by mounting the plurality of optical fibers in aresin ferrule, and a spacer for forming the gap is provided in theadapter of the optical fiber connecting structure.